A Danish skoenvirke brooch

made of silver and decorated with two blue stones (lapis or agathe?).
Engraving on the back saying “Tak fra” (thank you from). The brooch was originally half of a belt buckle.
Maker´s mark: SJ. Probably made by Evald Nielsen who worked for SJ before starting his own workshop. 

Width: 7,5 cm
Height: 6 cm.